| Abstract: | Ventilatory responses to carbon dioxide (Sco2) were measured in 15 asymptomatic asthmatic patients in whom CO2 retention had been documented during a previous attack of acute asthma. At the time when Sco2 was measured, the patients had normal or only mildly impaired ventilatory function (vital capacity (VC) 3,5 +/- 0,19 I, 98,7 +/- 4% of predicted (mean +/- SE); forced expiratory volume in 1 second (FEV1) 2,37 +/- 0,161, 83,8 +/- 5,2% of predicted; and FEV1/VC 68 +/- 2,5%). Fifteen control subjects without lung disease were also studied (VC 4,38 +/- 0,28 I, 103 +/- 2,6% of predicted; FEV1 3,76 +/- 0,23 I, 112 +/- 4,4% of predicted; FEV1/VC 86 +/- 7,8%). Sco2 in the patients (1,21 +/- 0,14 l/min/mmHg, range 0,62 - 2,81) was significantly different (P less than 0,001) from that in controls (2,13 +/- 0,17 l/min/mmHg, range 1,13 - 3,17). Sco2 in a subgroup of 5 patients with normal pulmonary function was also significantly different from that in controls. Correction for lung size (Sco2/VC) did not detract from the significance of the difference between patients and controls, suggesting that inherently low respiratory centre sensitivities to CO2 may have played a role in the development of hypercapnia during severe asthma in these patients. |
